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Whirlwind Mine Groundwater Characterization Report <br /> The only other observed source was a seep emanating from the Wingate Sandstone. The <br /> streambed itself exhibited surface water within the lowest reach near the canyon's mouth. <br /> These observations support the conclusion that the hydrostratigraphy in the area of the <br /> Whirlwind Mine and downgradient areas do not provide sufficient groundwater flux to result in <br /> perennial stream flow. <br /> 4.2 Hydrogeology <br /> Knowledge of groundwater occurrence at the Whirlwind Mine and surrounding area has <br /> progressed over the last several decades, primarily as a result of historical mining operations <br /> and the"need to know" as a result of current state mining and public health and environmental <br /> regulations associated with mining activities. <br /> Groundwater occurrence has been observed primarily through the drilling of the more recent <br /> exploration boreholes, underground mine workings, monitoring wells, water wells, springs, and <br /> one groundwater investigation borehole. These observations are summarized and re- <br /> documented in this section of the report. <br /> The geology of the Whirlwind Mine and vicinity was summarized in the Section 3.1. As such, the <br /> geologic section at the mine consists, from youngest to oldest, of the Cretaceous-age Dakota <br /> Sandstone(50 ft thick), the Burro Canyon Formation (105 ft thick), the Jurassic-age Morrison <br /> Formation comprised of the Brushy Basin Member (405 ft thick) and the Salt Wash Member <br /> (300+ ft thick), the Summerville Formation (90 ft thick) and the Entrada Sandstone (250 ft thick) <br /> (Cater, 1955). Over 800 ft of primarily Triassic-age sedimentary rocks underlie the Entrada <br /> Sandstone and are well-exposed in the deep canyons east of Whirlwind Mine. <br /> Groundwater-bearing zones are known to occur in the following hydrostratigraphic units: <br /> • The lower-most Burro Canyon Formation, <br /> • A middle Brushy Basin zone, <br /> • A lower Brushy Basin zone, and <br /> • The upper-most sandstone unit (Top Rim) of the Salt Wash (by some reports). <br /> Western Water& Land, Inc. 13 <br />